The liquid crystal display market has experienced rapid growth in many applications such as clocks, cellular phones, personal digital assistants (PDAs), notebook PCs, PC monitors, DVD players, and TVs. Liquid crystal display devices use liquid crystal switching to visualize the polarization state, and on the basis of the display principle, they use polarizers.
For example, iodine-based polarizers composed of stretched polyvinyl alcohol and iodine adsorbed thereto are most popular polarizers widely used because of their high transmittance and high degree of polarization. Such polarizers have disadvantages such as extremely weak mechanical strength and heat or water shrinkability, which can cause a significant reduction in polarizing function. Therefore, immediately after produced, a polarizer is bonded to an adhesive-coated protective film with the adhesive interposed therebetween, and the resulting polarizing film is used for applications.
On the other hand, as image display devices such as liquid crystal display devices have been reduced in thickness, polarizing films have also been required to be thin. In the process of producing a thin polarizer, the polarizer can be damaged because of its small thickness. Therefore, a carrier film (removable protective film) is used in the production of a thin polarizer. For example, a thin polarizer can be formed on such a carrier film by stretching and dyeing a laminate including the carrier film and a polyvinyl alcohol-based resin layer formed on one side of the carrier film (Patent Documents 1 to 6). A one-side-protected polarizing film can also be used, which includes a polarizer and a protective film provided on only one side of the polarizer, being free of any protective film on the other side. Such a one-side-protected polarizing film can be thinner than a double-side-protected polarizing film including a polarizer and protective films provided on both surfaces of the polarizer, because the former has one less protective film than the latter.